On a spring day in 1820, a young boy named Joseph Smith prayed to know which church to join. God the Father and His Son, Jesus Christ, appeared to him. Calling Joseph by name and pointing to Jesus, Heavenly Father said, "Joseph, this is my Beloved Son. Here Him!" Jesus told Joseph that none of the churches on the earth were completely true; "They draw near unto me with their lips, but their hearts are far from me," He said. Rather than join an existing religion, Jesus said that Joseph would be an instrument in the hands of Heavenly Father in the restoration of Christ's true church, just as it was when He was on the earth. (After Jesus' death, the apostles He had called died or were killed. This was the beginning of what is known as the great apostasy, or a time of spiritual darkness and lack of priesthood authority on the earth. Click here to learn more.)
Ten years later, in 1830, The Church of Jesus Christ of Latter-Day Saints was organized.
I know that Joseph Smith was and is a prophet called by Heavenly Father to restore the gospel in its fulness to the earth. If you read The Book of Mormon, you can know it too. This is my testimony.